Academic literature on the topic 'Sexually deceptive'

Caladenia is very unusual in that it contains species that attract pollinators by two different strategies, food and sexual deception. Among the sexually deceptive species, baiting for pollinators has shown that within populations orchid species are typically pollinated by a single species of thynnine wasp. However, some wasp species can be pollinators of more than one species of orchid usually when their ranges do not overlap. There is a trend for closely related orchids to exploit wasps from the same genus, with different lineages of orchids often pollinated by different genera. Very little is known about pollination of food-deceptive Caladenia species, although it is evident they attract a suite of generalist food-seeking insects. Food-deceptive species have a higher pollination rate than do sexually deceptive species. Studies of population genetics and pollen movements are few, although they suggest a pattern of fine-scale genetic structuring within populations, owing to predominantly restricted seed dispersal and low genetic differentiation among populations as a consequence of rare long-distance seed-dispersal events. Both evolutionary and ecological research of Caladenia will greatly benefit from a better understanding of the insect species involved in pollination, their ecological requirements and the ecological and genetic consequences of food and sexual deception.

The costs that species suffer when deceived are expected to drive learned resistance, although this relationship has seldom been studied experimentally. Flowers that elicit mating behaviour from male insects by mimicking conspecific females provide an ideal system for such investigation. Here, we explore interactions between a sexually deceptive daisy with multiple floral forms that vary in deceptiveness, and the male flies that pollinate it. We show that male pollinators are negatively impacted by the interaction, suffering potential mating costs in terms of their ability and time taken to locate genuine females within deceptive inflorescences. The severity of these costs is determined by the amount of mating behaviour elicited by deceptive inflorescences. However, inexperienced male flies exhibit the ability to learn to discriminate the most deceptive inflorescences as female mimics and subsequently reduce the amount of mating behaviour they exhibit on them with increased exposure. Experienced males, which interact with sexually deceptive forms naturally, exhibit similar patterns of reduced mating behaviour on deceptive inflorescences in multiple populations, indicating that pollinator learning is widespread. As sexually deceptive plants are typically dependent on the elicitation of mating behaviour from male pollinators for pollination, this may result in antagonistic coevolution within these systems.

Abstract Sexual deception involves the mimicry of another species’ sexual signals in order to exploit behavioural routines linked to those signals. Known sexually deceptive systems use visual, acoustic or olfactory mimicry to exploit insects for prédation, cleptoparasitism and pollination. It is predicted that where sexual deception inflicts a cost on the receiver, a coevolutìonary arms race could result in the evolution of discriminating receivers and increasingly refined mimicry. We constructed a conceptual model to understand the importance of trade-offs in the coevolution of sexually deceptive mimic and receiver. Four components examined were: the cost of mimicry, the cost to receiver for being fooled, the density of mimics and the relative magnitude of a mimicry-independent component of fitness. The model predicts that the exploitation of non-discriminating receivers by accurate signal mimicry will evolve as an evolutionary stable strategy under a wide range of the parameter space explored. This is due to the difficulty in minimising the costs of being fooled without incurring the cost of falsely rejecting real mating opportunities. In the model, the evolution of deception is impeded when mimicry imposes substantial costs for both sides of the arms race. Olfactory signals that are potentially cheap to produce are therefore likely to be more vulnerable to exploitation than expensive visual ornaments.

Orchids of the genus Caladenia have been shown to utilise two quite different pollination strategies, namely species-specific sexual deception of thynnine wasps and a more generalist strategy attracting a larger spectrum of foraging insects. While baiting techniques have enabled the identification of numerous pollinators of sexually deceptive Caladenia, insects that pollinate food-advertising species have received little attention. The present study employed a multidisciplinary approach to better evaluate the pollination syndrome of the white spider orchid, Caladenia rigida R.S.Rogers, a species previously reported to utilise both food and sexual deception. This included the observation and capture of potential pollinators of C. rigida through direct observation, pantraps, Malaise traps and pollinator-baiting experiments, and the use of molecular techniques to identify orchid pollinia isolated from carrier insects. We describe a suite of generalist insects visiting and bearing pollinia from C. rigida. In addition, samples collected from the labellum and column of C. rigida contained sugars at levels comparable to those of a known nectar-producing orchid, Microtis parviflora R.Br. Potential osmophores in the clubs and calli stained positively with neutral red and although this character is often associated with sexual deception, we found no evidence for this secondary pollination syndrome in C. rigida. The present study is the first one to provide a detailed description of the pollinators and pollination syndrome of a non-sexually deceptive species within the genus Caladenia and the first report to provide evidence of nectar production by a species within this genus.

Pollinator-mediated selection has been suggested to play a major role for the origin and maintenance of the species diversity in orchids. Sexually deceptive orchids are one of the prime examples for rapid, pollinator-mediated plant radiations, with many species showing little genetic differentiation, lack of postzygotic barriers, but strong prezygotic reproductive isolation. These orchids mimic mating signals of female insects and employ male insects as pollinators. This kind of sexual mimicry leads to highly specialised pollination and provides a good system for investigating the process of pollinator-driven speciation. Here, we summarise the knowledge of key processes of speciation in this group of orchids and conduct a meta-analysis on traits that contribute to species differentiation, and thus potentially to speciation. Our study suggests that pollinator shift through changes in floral scent is predominant among closely related species in sexually deceptive orchids. Such shifts can provide a mechanism for pollinator-driven speciation in plants, if the resulting floral isolation is strong. Furthermore, changes in floral scent in these orchids are likely controlled by few genes. Together these factors suggest speciation in sexually deceptive orchids may happen rapidly and even in sympatry, which may explain the remarkable species diversity observed in this plant group.

It has recently been discovered that novel di-, tri- and tetra- substituted pyrazines are semiochemicals in Drakaea, an orchid genus that secures pollination by the sexual deception of male thynnine wasps. We examined if similar pyrazines were also present in the distantly related Caladenia barbarossa, a sexually deceptive orchid that is also pollinated by a thynnine wasp. Here we report for the first time the occurrence of two pyrazines, (3,5,6-trimethylpyrazin-2-yl)methyl 3-methylbutanoate (1) and 3-(3-methylbutyl)-2,5-dimethylpyrazine (2) in the orchid genus Caladenia. The former is known as a semiochemical involved in pollinator attraction in Drakaea livida. This convergence of floral odour between distantly related plants provides an exciting opportunity to understand the evolution and molecular basis of this sophisticated chemical mimicry.

The pollination of 20 common terrestrial orchids was studied in a 60-ha urban banksia and eucalypt dominated woodland in Western Australia. Five years of data (24,000 flowers, 6800 plants) measured fruit set relative to floral areas, capsule volumes, climate, phenology, pollination mechanisms, disturbance tolerance and demography. Pollination varied from 0–95% of flowers, floral displays from 90–3300 mm2 and capsules from 15–1300 mm3 per spike. Pollination traits strongly influenced outcomes, with self-pollination highest (59—95%), followed by sexually deceptive autumn or winter-flowering (18–39%), visual deception (0–48%) and sexually deceptive spring-flowering (13–16%). Pollination was limited by drought in autumn or spring and cool winter temperatures. Some orchids were resilient to drought and one formed seed after the leaves withered. Plant density had the greatest impact on fruit set for orchids forming large groups, especially for sexually deceptive pollination. Consequently, small group average (SGA) pollination was up to 4× greater than overall averages and peak seed production occurred in the best locations for genetic exchange and dispersal. SGA rates and seedpod volumes were strongly linked to clonality, but not to demographic trends. Resource competition limited flowering at higher plant densities and competition within spikes resulted in smaller, later-forming seedpods. Pollination data from co-occurring common orchids identified five evolutionary trade-offs linked to pollination, provided baseline data for rare species and revealed impacts of changing climate.

Australia is a major centre of diversity for pollination by sexual deception, a pollination syndrome unique to orchids and characterised by highly specific pollinator relationships. Chiloglottis pescottiana is a rare natural hybrid between sexually deceptive C. trapeziformis and C. valida. We utilised bioclimatic models to predict the potential range of the parental orchid species, the hybrid and their pollinators. The predicted ranges of the parental orchid species rarely overlapped (only 2% of the core range), with the geographic separation of the species reflecting the occupation of largely distinct climatic niches and limiting opportunities for hybridisation. Comparison of the predictions with independent distributions of the orchid taxa revealed a close match. Unexpectedly, our results revealed that several related and morphologically similar orchid species are, nevertheless, ecologically distinct from C. valida. Our study demonstrates that bioclimatic modelling provides an additional tool for exploring a range of ecological and evolutionary questions.

A presente dissertação pretende contribuir para o aumento do conhecimento numa área específica da polinização em orquídeas, designada como polinização deceptiva (sexual deception) usando a espécie Ophrys fusca como modelo. Tendo por base 100 labelos de 100 plantas diferentes, colhidas no seu habitat natural, recorreu-se a técnicas de transcritómica e metabolómica com o objectivo de (1) analisar a expressão génica por microarrays de cDNA após a polinização; (2) proceder à caracterização metabólica por cromatografia gasosa e espectrometria de massa (GC-MS). Os resultados obtidos permitiram contribuir para a compreensão dos mecanismos de polinização por sexual deception, nomeadamente no que respeita às características do labelo (ex. pigmentação, emissão de compostos), dos processos de senescência ou da biologia floral das orquídeas. A construção de um chip de cDNA para O. fusca permitirá realizar hibridações com outras espécies de Ophrys, possibilitando a determinação do grau de conservação dos mecanismos genéticos na polinização por sexual deception; ABSTRACT:This work aims at contributing to the knowledge on orchid pollination biology, through the study of the peculiar pollination mechanism of Ophrys fusca by sexual deception. In this mechanism, Ophrys labellum mimics the female sex pheromones thereby deceiving male pollinators that attempt to copulate with the orchid labellum. Labellum transcriptome analysis by a custom-made cDNA microarrays allowed to verify gene expression modulation of post pollination changes. Processes involved in labellum morphology, petal senescence and pollination biology were adressed. A metabolic profiling by gas-chromatography mass- spectrometry was focused on compounds involved in Ophrys-pollinator crosstalk, in order to determine their dynamics after pollination. By means of both transcriptional and metabolic analysis, the work here presented gives an important contribution towards the understanding of orchid pollination biology by deceit. The custom-made cDNA chip may be useful for performing cross-species hybridization to track differences on transcripts modulation thereby disclosing the genetic basis underlying sexual deception; RESUMO:A família das orquídeas (Orchidaceae) inclui mais de 22 000 espécies, representando cerca de 10% das plantas com flor. A sua extraordinária diversidade floral reflecte a importância das relações planta-polinizador na evolução das orquídeas, sendo as diferentes estratégias de polinização consideradas como uma das razões para a diversificação e especiação na família. Os mecanismos de polinização em orquídeas sempre intrigaram os cientistas, incluindo Darwin. Uma das estratégias mais fascinantes na biologia destas plantas é a capacidade de polinização deceptiva, ocorrendo em cerca de 1/3 das espécies. A presença de uma pétala modificada, o labelo, tendo como função principal atrair insectos polinizadores, é igualmente uma das características mais distintivas das orquídeas. Os mecanismos de polinização deceptiva mais comuns incluem a imitação de flores que apresentam néctar (food deception), ocorrendo em 38 géneros; e a imitação de insectos-fêmea (sexual deception), abrangendo 18 géneros. O género Ophrys sempre foi considerado um modelo para estudo de polinização deceptiva, nomeadamente do caso de flores sexualmente deceptivas (sexual deception). As flores deste género emitem substâncias químicas idênticas às feromonas libertadas pelas fêmeas sexualmente receptivas dos insectos polinizadores, bem como apresentam características morfológicas (ex: forma, cor, pilosidade) que mimetizam o corpo dos insectos-fêmea. Os estudos desenvolvidos em polinização de orquídeas têm sido desenvolvidos nas áreas da biologia celular, micromorfologia, genética populacional, análise química e na determinação funcional de determinados genes, bem como em estudos bioquímicos e fisiológicos. Contudo, para a compreensão global de um processo são necessárias técnicas que permitam obter dados a larga escala. Este trabalho pretende constituir um contributo para o conhecimento dos mecanismos regulados pela polinização em orquídeas. Para tal, uma espécie de orquídea selvagem abundante em Portugal, Ophrys fusca Link, foi usada como modelo de estudo do mecanismo de polinização deceptiva (sexual deception). Para atingir o presente objectivo, foram aplicadas duas técnicas diferentes: a análise da expressão génica por microarrays de cDNA e a caracterização metabólica por cromatografia gasosa e espectrometria de massa (GC-MS). O labelo foi seleccionado como foco do estudo, dada a sua importância na emissão de compostos importantes na comunicação com o insecto polinizador e no processo geral de polinização em orquídeas. A amostragem foi efectuada em 100 labelos de 100 plantas diferentes no seu habitat natural, e seleccionaram-se dois tempos de estudo: 2 dias após a polinização (DAP) e 4 DAP.A análise do labelo por microrrays de cDNA permitiu verificar a modulação da expressão génica após a polinização. Com este estudo de larga escala conseguiu-se verificar que aos 2 DAP, o evento de polinização é reconhecido como uma resposta a um stress e aos 4 DAP, detectaram-se genes que indicam a mobilização de nutrientes bem como uma nova síntese proteica, necessária para a progressão específica da senescência do labelo. A polinização despoleta processos de proteólise, mobilização de nutrientes como o fosfato, carbono e azoto, e desactiva mecanismos energeticamente dispendiosos, como a fotossíntese e fotorespiração bem como as principais vias metabólicas que permitem manter a vitalidade do labelo. Os transcritos identificados revelam processos importantes do metabolismo secundário envolvidos em características do labelo (ex. pigmentação, emissão de compostos), em proteólise a larga escala (ex. proteases cisteínicas) e dirigida (ex. fosfatases e quinases), stress e defesa, além de vias associadas à mobilização de nutrientes. Inicialmente, a expressão génica de diversos transcritos descritos em situações de stress e de patogenicidade (ex. GST, proteínas Lea5, metalotioneínas tipos 2 e 3, quitinases, proteínas PR, proteases cisteínicas, RNases) indicam que a modulação da transcrição é regulada por vias não específicas de reconhecimento do evento de polinização, semelhantes a uma situação de stresse abiótico e/ou biótico. Contudo, aos 4 DAP, verificou-se a transcrição de genes associados à síntese proteica, indicando a activação de um novo processo de tradução de proteínas específicas que irão dirigir o labelo para a morte celular irreversível. A análise do perfil metabólico dos extractos dos labelos foi focada em compostos da cutícula, especificamente alcanos e alcenos, descritos como responsáveis por despoletar o comportamento de pseudocópula dos machos polinizadores. Os resultados demonstram que, após a polinização, a quantidade total dos compostos não diminui, estando de acordo com resultados anteriores observados em Ophrys sphegodes. Esta observação poderá dever-se à função que estes compostos desempenham, nomeadamente como parte integrante das camadas das ceras prevenindo a desidratação. A análise do labelo após a polinização por microarrays permitiu a identificação de transcritos, nomeadamente duas sequências de stearoil ACP desaturase (SAD), envolvidos nas vias biossintéticas dos compostos da cutícula, importantes na interacção Ophrys-polinizador. A subexpressão destes transcritos em conjugação com a manutenção da produção do odor após a polinização indica que a correlação entre os níveis de expressão dos genes com os seus produtos de síntese não pode ser directamente efectuada. O estudo do labelo após a polinização por técnicas de proteómica irá permitirá a detecção das enzimas bem como alterações pós tradução importantes na regulação das proteínas. Esta abordagem irá possibilitar a compreensão da regulação das proteínas após o evento de polinização. O presente estudo permitiu obter uma visão geral no labelo dos mecanismos regulados pela polinização, contribuindo para a compreensão da polinização por sexual deception recorrendo a técnicas de Ó’micas. A análise do labelo através de técnicas de transcritómica e metabolómica após a polinização permitiu dar um importante contributo para a compreensão dos processos de senescência, características do labelo (ex. pigmentação, emissão de compostos), bem como da biologia floral das orquídeas. Além disso, a construção de um chip de cDNA construído especificamente para a orquídea em estudo irá permitir a realização de hibridações com outras espécies do mesmo género, possibilitando o estudo da conservação dos mecanismos genéticos na regulação dos eventos pós-polinização de orquídeas com flores sexualmente deceptivas; ABSTRACT:Orchidaceae family includes more than 22,000 species of plants, representing around 10 % of all flowering plants. The extraordinary floral diversity in orchids reflects the importance of plant-pollinator associations in their evolution, and pollination biology is regarded as a driving force in orchid diversification and speciation. Pollination biology in Orchidaceae has long intrigued evolutionary biologists, and interest in orchid pollination dates back to Darwin. The most fascinating in orchid biology is pollination by deception, occurring in approximately 1/3 of the species, being food (38 genera) and sexual (18 genera) deception the most common types. Sexual deception mechanism was first described in the European Ophrys genus by Pouyanne in 1917, and in this mechanism, Ophrys orchids mimic their pollinators’ mating signals, and are pollinated by male insects during mating attempts. Studies on orchid pollination have mainly focused on cell biology, population genetics, micromorphology, chemical analysis and gene-function studies, as well as biochemical and physiological studies on flowers. A general approach towards the understanding on orchid pollination biology, as well as in the events following pollination, by means of high throughtput techniques is lacking. The study here presented intends at contributing to the knowledge on post pollinationregulated mechanisms in the sexual deceptive orchid Ophrys fusca Link, a common bee orchid in the Mediterranean, natural occurring in Portugal. To accomplish such goal, two different approaches were assigned: a transcriptional analysis and a metabolic profiling. Transcriptomics and metabolomics were both used to gather insights on the post pollination changes occurring in Ophrys fusca labellum. To access pollination-enhanced events, two time points were considered for analysis: 2 and 4 days after pollination (DAP). Labellum transcriptional analysis allowed probing gene expression modulation of post pollination changes. The first response to pollination appears to be a stress response (2DAP) and later at 4DAP, nutrient mobilization occurs and de novo protein synthesis is induced for senescence progression. Pollination sets off proteolysis, remobilization of nutrients such as phosphate, carbon and nitrogen from labellum and deactivates energy-consuming processes (e.g. photosynthesis, photorespiration) and major metabolic pathways related to labellum upholding. Transcripts identified by microarray analysis reveal pivotal processes associated with secondary metabolism responsible for labellum traits (e.g. pigmentation, compounds emission involved in pollination), proteolysis, stress and defence, and remobilization of nutrients associated with pollination induced-senescence. Labellum transcriptional regulation seems to be mediated by non-specific stress-related pathways, disclosed by the expression of several stress- and pathogen-related transcripts (GST, antimicrobial snakin proteins,Lea5 protein, metallothioneins types 2 and 3, chitinases, PR protein, Cys proteases, RNases), until the newly protein synthesis is achieved for senescence progression. Metabolic profiling in labella extracts was focused on cuticular compounds (alkanes and alkenes), known to trigger the pseudocopulatory behaviour of male pollinators. Results show that post pollination machinery does not rely on an abrupt decrease of odour production, which is in agreement with previous reports on other Ophrys species, probably due to compounds function as part of the desiccationpreventing wax layers. Through labellum gene expression analysis, transcripts related to biosynthetic pathways of cuticular compounds, involved in Ophrys pollinator attraction, were identified: stearoyl ACP desaturases (SAD). Down regulation of these transcripts along with maintenance of odour production may indicate that correlation between RNA level and its by-products cannot be directly made. Thus, a labellum post pollination proteomics approach will allow tracking enzymes responsible for alkenes’ production, thereby giving a more comprehensive walkthrough of their regulation on pollination event. Such observations could adjoin some awareness on the genetic basis of pollinator attraction. By combining both transcriptional and metabolic profiling analysis to study post pollination events in a sexually deceptive orchid, the work here presented gives an important contribution for the understanding of this peculiar pollination system.

Risky sexual practices can lead to concerning public health issues, including sexually transmitted infections (STIs) and unintended pregnancy. Coercive or deceptive behaviors by one’s partner to engage in risky practices may be one factor contributing to sexual risk. This study examined experiences of sexual risk coercion and deception, including partner sexual infidelity, coerced condom nonuse, and fear of negative partner reaction to condom request, as predictors of engagement in sexual risk behaviors, including condom use, safer sex communication, and lifetime number of sexual partners. Self-esteem was examined as a moderator. College students (N = 216) were recruited through the ETSU Sona System to complete self-report surveys via the REDCap survey platform. Using SPSS, linear regression analyses and PROCESS moderation analyses were performed. In analyses of covariance, gender, race/ethnicity, and sexual orientation made no significant contributions to the models. Partner sexual infidelity significantly predicted lifetime number of sexual partners (F(1, 210) = 11.042, p = .001, β = 3.088, SE = .929), R2 = .050. Self-esteem was found to be a significant moderator of this relationship (F(1, 197) = 8.759, p = .0035). Fear of negative partner reaction to condom request significantly predicted lifetime number of sexual partners (F(1, 213) = 4.930, p = .027, β = 2.609, SE = 1.175), R2 = .023. Future research should continue to examine the psychosocial determinants of sexual behaviors, as increased understanding will inform more effective sexual risk intervention to reduce HIV, other STIs, and unplanned pregnancy among college populations.

Background and Aims Sexual deception is a species-specific pollination strategy commonly found in Orchidaceae. Sexually deceptive orchids lure male insect pollinators by mimicking the sex pheromones and/or appearance of female insects, which elicit copulatory behaviour with the flower by the male insects. This specialised pollination strategy has recently been found in a Pterostylis species in Australia. Pterostylis orchids also occur in New Zealand, although very few studies have been done on this genus, and no such specialised insect pollination strategy has been documented in New Zealand. Methods I investigated the breeding system and pollinators of three Pterostylis spp. to determine whether sexual deception may be operating in P. oliveri, P. irsoniana and P. venosa growing in native beech forests in Arthur's Pass. We also investigated the floral headspace volatiles of P. oliveri to determine which compounds are present, and which may be responsible for pollinator attraction. Key Results Breeding system experiments suggest that P. oliveri and P. irsoniana are self compatible, but exclusively dependent on insects for pollination. Only male fungus gnats (Diptera: Mycetophilidae) were found carrying pollinia attached to their thoraxes in traps set up over the flowers. Insect identification and ITS DNA analysis of the pollinia showed that each orchid species was pollinated by a specific fungus gnat species; Mycetophila latifascia males found with pollen of P. oliveri; Morganiella fusca males found with pollen of P. irsoniana; and Tetragoneura sp. males found with pollen of P. venosa. Field tests of an unidentified compound found in headspace volatiles of P. oliveri did not attract any Mycetophila latifascia males. Conclusions These results indicate that pollination via sexual deception may be operating in these three Pterostylis spp. However, further floral volatile analyses are required to confirm whether the flowers emit volatile compounds that resemble the sex pheromones of the specific pollinators.

Child maltreatment is extremely prevalent and leads to a host of negative effects, both immediately and long term. Instances of maltreatment are often accompanied by deception, both by the perpetrator, as well as by the victim in order to avoid stigma and protect family. Thus, this study investigated social learning of deception through instances of maltreatment. 413 young adults completed an online survey assessing current attitudes toward deception, childhood maltreatment including child sexual abuse, child physical abuse, witnessing interparental violence, psychological abuse, neglect and parental addiction, social support, and participant addiction. Results indicated that neglect and psychological abuse during childhood, and current addiction were associated with a positive attitude toward deception. Severity of CSA and severity of neglect each interacted with role (agent or target) in the deceptive scenario to determine attitude toward deception. Severity of CPA interacted with perceived social support to determine attitude toward deception. Furthermore, victim's awareness of deception by perpetrators of CSA was associated with a more negative attitude toward deception. These findings support both attachment theory and social learning explanations for adulthood attitude toward deception. Attachment theory explains why neglected and psychologically abused individuals find their own deception more acceptable and other's deception less acceptable than their non-neglected counterparts, and why the opposite pattern is true for victims of CSA; and social learning theory's emphasis on attention and reinforcement to motivate behavior are supported by these findings.

Cette thèse aborde l’écologie et l’évolution des relations qu’entretiennent les orchidées du genre Ophrys avec leurs pollinisateurs. L’approche comparative et la combinaison (i)

d’analyses chimiques de phéromones sexuelles et de parfums floraux, (ii) d’analyses génétiques avec des outils moléculaires, et (ii) de tests de comportement réalisés sur les insectes in situ nous ont permis d’éclairer certains aspects méconnus de ces interactions inter-spécifiques. La pollinisation des orchidées du genre Ophrys est assurée par des mâles d'abeilles ou de guêpes solitaires qui opèrent une tentative d’accouplement (pseudocopulation) sur le labelle des fleurs. L'attraction des pollinisateurs est généralement hautement spécifique, régie par un mimétisme des signaux (chimiques, visuels, tactiles) des femelles des espèces d'insectes concernés. Malgré cette spécificité, des hybrides se forment occasionnellement en conditions naturelles, témoignant de la perméabilité partielle des barrières d'isolement reproductif entre espèces. Au cours de

ce programme de recherche, nous avons entrepris l’étude des interactions Ophryspollinisateurs en mettant l’accent sur trois aspects spécifiques, à savoir (i) la sélection des caractères floraux par les pollinisateurs, (ii) l'isolement reproductif entre espèces d'Ophrys sympatriques, et enfin (iii) l'évolution des caractères floraux au sein d'un complexe d'espèces-soeurs d'Ophrys associées à différents pollinisateurs. Les principaux

résultats de ce travail sont repris ci-dessous, ponctués de références aux articles qui rassemblent l’intégralité des études réalisées.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Sexual deception, entailing the pollination of flowers through mimicry of female insects, is one of the most remarkable pollination strategies to have evolved. This thesis explores two Australian sexually deceptive orchid systems with contrasting patterns of pollinator exploitation. The first three chapters focus on the genus Cryptostylis, a system with a unique case of pollinator sharing - five Australian species, four of which are largely sympatric, all deceive the same male ichneumonid pollinator. In Chapter One, mark-recapture experiments were used to investigate the consequences of ichneumonid pollination on pollen movement in C. ovata. A high pollinator revisitation rate indicated some potential for self-pollination. In Chapter Two, reproductive barriers contributing to the absence of hybrids between Cryptostylis species were investigated. Pre-pollination barriers, assessed in field experiments, did not prevent hybridisation. Hand cross-pollinations conducted among the four common Cryptostylis species in a greenhouse all produced fruits, however seed mass and the percentage of formed embryos were reduced in hybrids. Major differences in ploidy and chromosome number likely explain this post-pollination fitness reduction. Two Cryptostylis species were found to be self-incompatible, marking the first case of self-incompatibility in the Diurideae. The unique reproductive biology of Australian Cryptostylis, encompassing pollinator sharing, self-incompatibility, and post-pollination reproductive isolation driven by large ploidy differences, may indicate that its mode of diversification may differ greatly to those in other sexually deceptive genera. Chapter Three presents the first phylogeny to encompass both Australian and Asiatic Cryptostylis. An Australian origin of Cryptostylis is supported, with a likely single dispersal event to Asia. Ploidy variation and geographic barriers appear to have played a role in diversification across Cryptostylis. In Chapter Four, the potential presence of pollination ecotypes in Drakaea livida was tested for. Patterns of chemical diversity and pollinator availability across the distribution of the species are investigated. Pollinator choice trials revealed the presence of three discrete ecotypes each attracting its own pollinator species. Patterns of pollinator availability did not correlate with ecotype distribution. Each ecotype possessed a significantly different floral volatile composition. Using Partial Least Squares Discriminant Analysis (PLS-DA), the presence-absence of a subset of taxonomically informative compounds could be used to accurately predict the ecotype of a flower. Different classes of electrophysiologically active compounds were present in different ecotypes. These marked differences in chemical composition between the ecotypes suggest either a long time since their divergence and may hint at a scenario of convergent evolution of floral morphology. In Chapter Five, the ecotype geographic ranges and methods of identifying the ecotypes were investigated. Species distribution modelling predicted each ecotype to have a different core range. Two ecotypes were widespread, while one had a limited distribution within extensively cleared agricultural land, raising conservation concerns. PLS-DA correctly identified the ecotype of a flower when labella extracts were made from pollinated flowers, thereby providing a non-destructive identification technique. The pollinator specificity, morphology, floral chemistry, and ranges of the ecotypes supported them as Evolutionary Significant Units. In conclusion, the ecological and evolutionary consequences of pollination by sexual deception may vary extensively between plant taxa in accordance with their different patterns of pollinator exploitation. The taxonomy, species richness of the pollinator group, and the plant species to pollinator species ratio all influence the evolution and diversification of sexually deceptive orchids.

There are few other structures in nature from which evolution has generated such wide diversity as the flower or inflorescence, and this diversity is commonly attributed to the influence of their animal visitors. By outsourcing their mate choice to pollinators, plants have left themselves - and especially their flowers - subject to the selective forces imposed by the behaviour, cognition and perception of the pollinators that serve them. The orchids provide some of the most remarkable and extreme examples of adaptations to specific animal pollinators. Perhaps one of the most peculiar of these strategies is sexual deception, whereby male insects are lured to the flower by mimicry of the female sex pheromone. This seemingly unlikely strategy has evolved multiple times independently on different continents in different parts of the orchid phylogeny which raises the question of what adaptive advantages might underlie such a strategy. This multidisciplinary thesis studies gene flow and pollinator behaviour in two sympatric sexually deceptive orchids in the genus Chiloglottis. The two species attract their specific wasp pollinators through emission of distinct species - specific semiochemicals. Since floral volatiles play a pre-eminent role in pollinator attraction, Chiloglottis provides an excellent case study for examining the interaction between floral volatile chemistry, pollinator behaviour and the evolutionary dynamics of populations. The thesis begins with a review of floral volatiles and their role in pollinator attraction and plant speciation. The literature is used to develop a research framework of six testable hypotheses under which we might productively explore the influence of floral volatiles on plant evolution. These hypotheses are then explored in the study system over the following chapters. A study of pollinator specificity, neutral genetic differentiation and floral chemistry demonstrates that the chemical mimicry crucial to sexual deception is responsible for reproductive isolation and potentially even speciation. Mating system and paternity analysis provide the first genetic evidence for multiple paternity in orchid broods. Extensive outcrossing is found to predominate and paternity assignment shows evidence for long distance pollen flow supporting the hypothesis that sexual deception promotes outcrossing and so minimizes the potentially deleterious effects of selfing. Lastly, an innovative new method is developed for tracking wasps in the field. Application of this technique to a population of orchid-pollinating wasps reveals detailed information about their movement and mating behaviour. The findings support the conclusion that sexual deception is a superb adaptive solution to the problem flowers face of simultaneously attracting pollinators and persuading them to leave quickly.

The work detailed in this thesis had its genesis in collaborative research efforts directed at understanding the ecological constraints on the evolution and speciation of sexually deceptive Chiloglottis orchids. Pollination by deception is a well documented phenomenon, particularly in the Orchidaceae, however only in recent decades has the chemical mimicry that so often drives these pollination syndromes become the subject of enquiry. This report commences with an outline of chemical mimicry and insect olfactory perception. Chapter 1 describes the conditions for pollination by food fraud and reproductive deception, with reference to insect pheromone systems, including their biological and behavioural functions, and chemical properties. Sexual deception, with a focus on the Australian genera, is given particular emphasis. A number of synthetic routes for the construction of 2,5-dialk(en)yl-1,3-cyclohexanediones, which represent insect sex attractants are reported in Chapters 2 and 3. Chiloglottones are natural products that operate both as female sex pheromones in thynnine wasp species as well as deceptive allomones in Chiloglottis orchids. We developed and utilised two alternative approaches to successfully make a diverse array of chiloglottone analogues (Chapter 2). These routes have been disclosed in publications as indicated in the Author's Declaration (page ii). Chapter 3 reports a case study of mimetic chemistry of the sexually deceptive orchid C. turfosa, which presented diverse synthetic challenges that required the design of new approaches towards the target 2,5-dialkyl-1,3-cyclohexanediones. Chapter 4 considers the interpretation of mass spectral data via high resolution analysis of synthetic 2,5-dialkyl-1,3-cyclohexanediones. This work, which was generated in cooperation with collaborators in Germany and has been reported in Proceedings of the National Academy of Sciences (see page ii), enables the rapid identification of likely structures from the mass spectra of new natural products that contain the 2,5-dialkyl-1,3-cyclohexanedione skeleton. This Chapter also describes our efforts to divulge the biosynthetic origin of chiloglottones in sexually deceptive Chiloglottis orchids. We discuss our journey towards revealing the circumstances required for in vivo chiloglottone biosynthesis, from the preparation of stable isotope labelled precursors, to manipulation of conditions for biosynthesis. The ecological conclusions that were revealed through our appreciation of the chiloglottones from some 20 Chiloglottis orchid species are described in Chapter 5. This includes the discovery of further natural products and the analytical and field evaluation of synthetic material. The relationship between orchid chemistry and phylogeny suggests that pollinator driven selection is a probable means of speciation in this taxon.